RCW 46.04.186: Fixed load vehicle.

"Fixed load vehicle" means a commercial vehicle that has a structure or machinery permanently attached such as, but not limited to, an air compressor, a bunk house, a conveyor, a cook house, a donkey engine, a hoist, a rock crusher, a tool house, or a well drilling machine. Fixed load vehicles are not capable of carrying any additional load other than the structure or machinery permanently attached.